1. Field of the Invention
The present invention relates to a control apparatus of an electric motor, which is used for an electric pump for a drive-train (a transmission) and a control method of the electric motor.
When the periphery of the transmission is subjected to a high temperature, a winding wire of the motor is also subjected to a high temperature (not less than 150° C.) so as to cause adverse effects on duration of life of the motor. In order to prevent such adverse effects, the following apparatus for protecting the motor has been known.
Conventionally, as described in Patent Document 1 (Japanese Patent-Application Laid-Open No. 05-137383), the motor is protected by using a temperature sensor to convert temperature change of the motor into a voltage and outputting it. By automatically stopping the operation of this motor when the temperature of the motor rises so as to hold the stopping state, a reliability of the protection operation against rise in temperature is improved. In addition, a motor control apparatus with a temperature sensor has been known because this motor control apparatus can arbitrarily and easily set the motor temperature where the protection device is operated by adjusting a reference voltage of a comparator to compare the reference voltage with the output voltage of the temperature sensor.
The apparatus for controlling the motor by detecting a temperature by means of the temperature sensor described in Patent Document 1 has the following problems. It is difficult to attach a temperature sensor to a motor stator. A process and a cost for attaching the temperature sensor are needed.
Since a lead wire of the temperature sensor is required to be attached to a driver, the number of man-hour for assembly is increased.